1. Field of the Invention
This invention relates to switches for electric power distribution systems. More particularly, it relates to a safety switch with an arrangement which assures positive operation of the spring toggle mechanism of such a switch.
2. Background Information
Safety switches are used in electric power distribution systems to isolate a load or a portion of the circuit. Typically, they include a switch mechanism housed in a sheet metal box. The switch mechanism has a number of switchblades mounted along a rotatable switch shaft. The shaft is rotated by a handle mounted at one side of the box and coupled to the shaft by a spring toggle mechanism which assures, by snap action, that the switch opens and closes rapidly. While such switches work very well under normal conditions, it is possible that the spring toggle linkage may not be able to effect the switching operation under some conditions, such as where the contacts become welded. This is a condition which can occur, for instance, in closing on a short circuit.
There is a need, therefore, for an improved safety switch of the type having a spring toggle linkage.
There is a particular need for such a safety switch with a capability of breaking any weld that might form between switch contacts.
More specifically, there is a need for such a safety switch which provides a direct mechanical coupling between the handle and the switch mechanism as the switch contacts open or close in addition to the coupling provided by the spring toggle linkage.
These needs and others are satisfied by the invention which is directed to a safety switch which is provided with a lost motion coupling between the handle and the switch shaft of the switch mechanism in addition to the spring toggle linkage. This lost motion coupling provides a direct mechanical connection between the handle and the switch shaft which is effected as the spring toggle linkage approaches the over center position.